High-temperature fan



C. NYGREN HIGH-TEMPERATURE FAN Jqne 21, 1949.

3 Sheets-Sheet 1 Filed March 15, 1946 June 21, 1949. Q NYGREN 2,473,813

' HIGH-TEMPERATURE FAN Filed March 15, 1946 3 Sheets-Sheet 2 I June 21, 1949. I C. NYGREN 2,473,813

HIGH-TEMPERATURE FAN Filed March l5, 1946 I 5 Sheets-Sheet 3 Patented June 2 1, 1949 UNITED HIGH-TEMPERATURE FAN Carl Nygren, Michigan City, Ind., assignor to Michiana Products Corporation, a corporation of Indiana Application March 15, 1946, Serial No. 654,714

4 Claims. 1

This invention relates to centrifugal fans or blowers for heat treating furnaces and the like, and has for its principal object to provide a simple construction in which preformed blades and side pieces are secured together and centered by means concentrically arranged about the axis of rotation whereby dynamic balance is made and preserved.

The particular design shown in the drawings is made to take advantage of available sheet material of suitable heat resisting alloys, but the general scheme of construction is equally applicable to cast parts, or a mixture of cast and sheet metal parts.

Figs. 1 and 2 are diagrammatic views of a conventional arrangement for a double inlet fan and associated parts;

Fig. 3 is a part side elevation and part cross section through a double inlet fan embodying this invention;

Fig. 4 is a part edge elevation and part axial section of the same fan and associated inlet cones;

Fig. 5 blades;

Fig. 6 is a perspective view of one of the bars used in this design to secure the blades;

Fig. 7 is a perspective view of one of the hub members; and

Fig. 8 is a perspective view of one of the pins by which the bars, shown in Fig. 6, are made fast to the hub shown in Fig. 7.

But these specific drawings and the corresponding description are used for the purpose of disis a perspective view of one of the closure only and are not intended to impose unnecessary limitations on the claims.

In Figs. 1 and 2, 10 indicates a conventional form of masonry installation for a fan or blower within which is a metal casing H for a double inlet fan 12 mounted on a hollow shaft [3, journalled in bearings l4 and driven by a motor I5 through a V-belt drive l6. Water cooling is ordinarily used in fan constructions for propelling high temperature fluids, such as the gases recirculated in the heat treating furnaces. In this arrangement, the inlet side of the watercooling unit is shown generally at IT, and the outlet side at Iii.

The detail of the double inlet fan is shown in L Figs. 3-7 (sheets 2 and 3). p l.

The fan is composed of twelve blades 20, two side plates 2 I. two hub members 22, on which are screw threaded two hub flanges 23 grooved on the inside at 50, twelve blade retaining bars 24, one

2 for each blade 20, and 24 securing pins 25, assembled on the hollow shaft l3.

Each side plate 2i is generally circular and flat, and has twelve openings 26 in annular series adjacent to its inner periphery to receive the reduced outer ends 21 of the pins 25.

Each blade is formed from a sheet substantially rectangular in original shape, having its inner portion given what will be called for want of a better term a return bend 28, giving each blade a sector-shaped inner portion, the twelve of which, when assembled, form a complete annulus about the shaft (Fig. 3). One of the bars 24 fits in each return bend sector-shaped inner portion of the corresponding blade and has openings 29 to receive inwardly directed reduced extensions 30 on pins 25.

outwardly with respect to the return bend portions 28, each blade is curved, as indicated generally at 3|, toward the direction of drive, and the extreme outer portion of each blade has another slightly different return bend 32, which provides in effect a cross bar having shoulders 33 received in notches 34 in the periphery of the side plates 2|.

The tolerances between the pins 25 and the associated hub members, side plates, and bars 2 1 are very close-on the order of .002"--from which number and arrangement of the pins it will be apparent that the several parts of the fan, particularly the blades and the side plates, are connected together, centered with respect to the axis of rotation, and securely made fast against independent outward movement under centrifugal force or otherwise, whereby with those parts properly formed and assembled the fan is given dynamic balance, and that is preserved during expansion and contraction in use.

Each of the side plates has six inlet openings 35, one wall of each of which is provided with a blade 35 formed of the metal of the side piece and shaped to provide an inwardly directed impeller for forcing air or gases into the fan. The shape of these impellers, as the shape of the blades will vary with individual ideas of engineers and the design for a particular purpose, but the shapes illustrated will serve as examples.

By reference to Fig. 4, it will appear that the outer edges of the impeller blades 36 are closely related to the adjacent edges of the inlet cones 31; and, while this relation is somewhat diagrammatic, it shows one arrangement that has been found satisfactory, and by a little juggling of the inlet cones and vanes a maximum intake of the fan will be effected.

From Fig. 3, it will appear that the inner curved portion of each blade crosses the corresponding inlet close to the leading edge of the corresponding impeller 36. In that area, as indicated at 38 (Fig. 4), each blade is cut away on a cru-ve and an incline to a narrow inner width 39 in order to provide ample inlet passage into the fan between adjacent blades and in advance of the impelling curved face of each blade.

The outer face of each hub flange member 23 is curved at 40 to prevent turbulence of the inlet air or gas, and all adjacent parts are shaped to ease the passage of the air for the same reason.

In this instance, each of the hub members 22 is keyed to the shaft I3 at M for driving; and ordinarily three keys, equally spaced around the circle, will be used in order to further insure dynamic balance. The hub member at the right in Fig. 4 rests against a collar 42, which in turn fits against a shoulder 43 on the shaft l3. The hub member at the left is made secure by a nut 44, which serves to fasten the entire assembly against the shoulder 43. The nut is made secure by a lock nut 45 and a lock washer 46 of familiar form and arrangement.

The particular design shown in these drawings is for a 15-inch fan in which the blades and side plates are made of alloy sheets of suitable heat resisting material, of which there are a number of chrome nickel alloys known to engineers and metallurgists.

In this design, each side plate 2! is 15 inches outside diameter and 2% inches inside diameter. The inlet openings 35 are 9 inches outside diameter and 4% inches inside diameter, which latter is the same as the outside diameter of the hub members 22. The pins 25 are 1%,- inches diameter with one-half inch projections. The long one is 1 inch, and the short one is inch. The blades 20 are 10 inches long between the side plates at the periphery and 8% inches long at the hub members. They are made of inch sheet. The notches 34, and therefore the shoulders 33, are 30 degrees apart. 4 The bottoms of the notches are degrees to the radius and are inch wide. The shoulders correspond, and, while accurate fitting is desirable, the fastening effected by the pins 25 preserves dynamic balance regardless of the fit of the parts near the periphery.

The side plates are also made of 4; inch material of heat resisting characteristics corresponding to the blades. The hub parts and the bars are made of the same or like material. The shaft is made of mild steel S. A. E. 1020, or equivalent.

These specific data are given to make the disclosure complete without intending to impose any unnecessary limitations on the claims.

While the drawings here show but the single key M, in practice three keys (substantially as lustrated in the application of Carl Nygren Ser. No. 533,456, filed May 1, 1944, now Patent No. 2,415,033) will be used.

The vanes 36 in connection with the inlet openings 35 and the cones 31 serve to very materially reduce, if not entirely eliminate, losses by turbulence of the air. In some fan constructions, turbulence in this general area accounts for a loss of about 10%. By proper arrangement and design of the parts 35, 36, and 31 in connection with the blades 20, this can always be materially reduced, and in most instances practically eliminated.

I claim:

1. In a centrifugal fan, a plurality of blade elements each having a blade member provided 4 at its inner end with a return bent portion radially shorter than the blade member and forming therewith an open channel of substantially sector shape, each return bent portion being engaged with the blade member of an adjacent blade element whereby the plurality of blade elements are assembled in circular series about a common axis of rotation, a pair of side plates, one at each side of the assembled blade elements, connected with the blade members adjacent to the outer edges thereof, hub members interposed between the ends of said channels and the inner portions of said side plates, a retaining bar positioned in each channel, and means securing said retaining bars and said inner portions of the side plates to said hub members.

2. In a centrifugal fan, a plurality of blade elements each having a blade member provided at its inner end with an integral return bent portion radially shorter than the blade member and forming therewith an open channel of wedge shape in cross section, each return bent portion being engaged with the blade member of an adjacent blade element whereby the plurality of blade elements are assembled in circular series about a common axis of rotation, a pair of side plates, one at each side of the assembled blade elements, connected with the blade members radially beyond the channels thereof, hub members concentric with the axis of rotation at the ends of the channels, a retaining bar positioned in each channel, and means securing the retaining bars and inner portions of the side plates to the hub members.

3. In a centrifugal fan, a plurality of blade elements each having a blade member provided at its inner end with a return bent portion and forming therewith an open channel of wedge shape in cross section, each return bent portion being engaged with the blade member of an adjacent blade element whereby the plurality of blade elements are assembled in circular series about a common axis of rotation, a pair of side plates, one at each side of the assembled blade elements, connected with the blade members near their outer periplieries and having center openings for admitting air or other fluid to the assembly of blade elements, hub. members concentric with the axis of rotation at the ends of the channels, a retaining bar positioned in each channel, means securing the retaining bars and inner portions of the side plates to the hub members, and a vane extending axially outwardly from each side plate adjacent to each opening therein for forcing air or other fluid through said opening.

4. In a centrifugal fan, a plurality of blade elements each having a blade member provided at its inner end with a. return bent portion and forming therewith an open channel of wedge shape-in cross section, each return bent portion being engaged with the blade member of an adjacent blade element whereby the plurality of blade elements are assembled in circular series about a common axis of rotation, a pair of side plates, one at each side of the assembled blade elements, connected with the blade members near their outer peripheries and having center openings for admitting air or other fluid to the assembly of blade elements, hub members concentric with the axis of rotation at the ends of the channels, a retaining bar positioned in each channel,

means securing the retaining bars and inner portions of the side plates to the hub members, a

vane extending axially outwardly from each side plate adjacent to each opening therein for forcing air or other fluid through said opening, and an inlet cone concentric with the axis of rotation adjacent to each side plate for directing air or other fluid to said openings.

CARLNYGREN.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Ruble Dec. 13, 1892 Landis Apr. 20, 1909 Ljungstrom Jan. 9, 1934 McKee Sept. 13, 1938 Nygren Oct. 2, 1945 

